Facebook on Friday changed its policy to ban all private sales of guns through its platforms, said Shannon Watts, founder of Moms Demand Action for Gun Sense in America. Facebook will rely on users to report content that violates the new policy, Watts told Fast Company.

“In this country, we know that 40% of gun sales are through unlicensed dealers, without background checks,” Watts said, noting that licensed dealers, such as Dick’s Sporting Goods, would still be allowed to advertise guns on Facebook. She pointed out, however, that “licensed dealers don’t sell on Facebook.”

The new policy affects both Facebook and Instagram, which the company acquired in 2012.

In a statement to Reuters, Facebook’s head of product policy, Monika Bickert, said:

Over the last two years, more and more people have been using Facebook to discover products and to buy and sell things to one another. We are continuing to develop, test, and launch new products to make this experience even better for people and are updating our regulated goods policies to reflect this evolution.